Debug output tweaks in the Linux target backends

This adds/tweaks a few debug logs I found useful recently.

gdb/gdbserver/ChangeLog:
2015-03-24  Pedro Alves  <palves@redhat.com>

	* linux-low.c (check_stopped_by_breakpoint): Tweak debug log
	output.  Also dump TRAP_TRACE.
	(linux_low_filter_event): In debug output, distinguish a
	resume_stop SIGSTOP from a delayed SIGSTOP.

gdb/ChangeLog:
2015-03-24  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (linux_nat_resume): Output debug logs before trying
	to resume the event lwp.  Use the lwp's ptid instead of the passed
	in (maybe wildcard) ptid.
	(stop_wait_callback): Tweak debug log output.
	(check_stopped_by_breakpoint): Tweak debug log output.  Also dump
	TRAP_TRACE.
	(linux_nat_filter_event): In debug output, distinguish a
	resume_stop SIGSTOP from a delayed SIGSTOP.  Output debug logs
	before trying to resume the lwp.

4 files changed, 73 insertions, 25 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 43dda55..fc65c603 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2015-03-24  Pedro Alves  <palves@redhat.com>
+
+	* linux-nat.c (linux_nat_resume): Output debug logs before trying
+	to resume the event lwp.  Use the lwp's ptid instead of the passed
+	in (maybe wildcard) ptid.
+	(stop_wait_callback): Tweak debug log output.
+	(check_stopped_by_breakpoint): Tweak debug log output.  Also dump
+	TRAP_TRACE.
+	(linux_nat_filter_event): In debug output, distinguish a
+	resume_stop SIGSTOP from a delayed SIGSTOP.  Output debug logs
+	before trying to resume the lwp.
+
 2015-03-24  Joel Brobecker  <brobecker@adacore.com>
 
 	* gdbtypes.h (struct dynamic_prop_list) <prop>: Remove
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index d9bc729..396abcb 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,10 @@
+2015-03-24  Pedro Alves  <palves@redhat.com>
+
+	* linux-low.c (check_stopped_by_breakpoint): Tweak debug log
+	output.  Also dump TRAP_TRACE.
+	(linux_low_filter_event): In debug output, distinguish a
+	resume_stop SIGSTOP from a delayed SIGSTOP.
+
 2015-03-24  Gary Benson  <gbenson@redhat.com>
 
 	* linux-x86-low.c (x86_linux_new_thread): Moved to
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 4743f7b..e4c5420 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -562,7 +562,7 @@ check_stopped_by_breakpoint (struct lwp_info *lwp)
 		{
 		  struct thread_info *thr = get_lwp_thread (lwp);
 
-		  debug_printf ("CSBB: Push back software breakpoint for %s\n",
+		  debug_printf ("CSBB: %s stopped by software breakpoint\n",
 				target_pid_to_str (ptid_of (thr)));
 		}
 
@@ -585,8 +585,8 @@ check_stopped_by_breakpoint (struct lwp_info *lwp)
 		{
 		  struct thread_info *thr = get_lwp_thread (lwp);
 
-		  debug_printf ("CSBB: Push back hardware "
-				"breakpoint/watchpoint for %s\n",
+		  debug_printf ("CSBB: %s stopped by hardware "
+				"breakpoint/watchpoint\n",
 				target_pid_to_str (ptid_of (thr)));
 		}
 
@@ -595,6 +595,16 @@ check_stopped_by_breakpoint (struct lwp_info *lwp)
 	      current_thread = saved_thread;
 	      return 1;
 	    }
+	  else if (siginfo.si_code == TRAP_TRACE)
+	    {
+	      if (debug_threads)
+		{
+		  struct thread_info *thr = get_lwp_thread (lwp);
+
+		  debug_printf ("CSBB: %s stopped by trace\n",
+				target_pid_to_str (ptid_of (thr)));
+		}
+	    }
 	}
     }
 #else
@@ -2059,16 +2069,28 @@ linux_low_filter_event (int lwpid, int wstat)
 	{
 	  /* We want to report the stop to the core.  Treat the
 	     SIGSTOP as a normal event.  */
+	  if (debug_threads)
+	    debug_printf ("LLW: resume_stop SIGSTOP caught for %s.\n",
+			  target_pid_to_str (ptid_of (thread)));
 	}
       else if (stopping_threads != NOT_STOPPING_THREADS)
 	{
 	  /* Stopping threads.  We don't want this SIGSTOP to end up
 	     pending.  */
+	  if (debug_threads)
+	    debug_printf ("LLW: SIGSTOP caught for %s "
+			  "while stopping threads.\n",
+			  target_pid_to_str (ptid_of (thread)));
 	  return NULL;
 	}
       else
 	{
-	  /* Filter out the event.  */
+	  /* This is a delayed SIGSTOP.  Filter out the event.  */
+	  if (debug_threads)
+	    debug_printf ("LLW: %s %s, 0, 0 (discard delayed SIGSTOP)\n",
+			  child->stepping ? "step" : "continue",
+			  target_pid_to_str (ptid_of (thread)));
+
 	  linux_resume_one_lwp (child, child->stepping, 0, NULL);
 	  return NULL;
 	}
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 803bdf6..660dc8f 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1799,16 +1799,16 @@ linux_nat_resume (struct target_ops *ops,
   if (resume_many)
     iterate_over_lwps (ptid, linux_nat_resume_callback, lp);
 
-  linux_resume_one_lwp (lp, step, signo);
-
   if (debug_linux_nat)
     fprintf_unfiltered (gdb_stdlog,
 			"LLR: %s %s, %s (resume event thread)\n",
 			step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
-			target_pid_to_str (ptid),
+			target_pid_to_str (lp->ptid),
 			(signo != GDB_SIGNAL_0
 			 ? strsignal (gdb_signal_to_host (signo)) : "0"));
 
+  linux_resume_one_lwp (lp, step, signo);
+
   if (target_can_async_p ())
     target_async (inferior_event_handler, 0);
 }
@@ -2618,7 +2618,7 @@ stop_wait_callback (struct lwp_info *lp, void *data)
 
 	  if (debug_linux_nat)
 	    fprintf_unfiltered (gdb_stdlog,
-				"SWC: Delayed SIGSTOP caught for %s.\n",
+				"SWC: Expected SIGSTOP caught for %s.\n",
 				target_pid_to_str (lp->ptid));
 
 	  /* Reset SIGNALLED only after the stop_wait_callback call
@@ -2795,8 +2795,8 @@ check_stopped_by_breakpoint (struct lwp_info *lp)
 	    {
 	      if (debug_linux_nat)
 		fprintf_unfiltered (gdb_stdlog,
-				    "CSBB: Push back software "
-				    "breakpoint for %s\n",
+				    "CSBB: %s stopped by software "
+				    "breakpoint\n",
 				    target_pid_to_str (lp->ptid));
 
 	      /* Back up the PC if necessary.  */
@@ -2811,14 +2811,21 @@ check_stopped_by_breakpoint (struct lwp_info *lp)
 	    {
 	      if (debug_linux_nat)
 		fprintf_unfiltered (gdb_stdlog,
-				    "CSBB: Push back hardware "
-				    "breakpoint/watchpoint for %s\n",
+				    "CSBB: %s stopped by hardware "
+				    "breakpoint/watchpoint\n",
 				    target_pid_to_str (lp->ptid));
 
 	      lp->stop_pc = pc;
 	      lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
 	      return 1;
 	    }
+	  else if (siginfo.si_code == TRAP_TRACE)
+	    {
+	      if (debug_linux_nat)
+		fprintf_unfiltered (gdb_stdlog,
+				    "CSBB: %s stopped by trace\n",
+				    target_pid_to_str (lp->ptid));
+	    }
 	}
     }
 #else
@@ -2830,7 +2837,7 @@ check_stopped_by_breakpoint (struct lwp_info *lp)
 	 breakpoint instruction.  */
       if (debug_linux_nat)
 	fprintf_unfiltered (gdb_stdlog,
-			    "CB: Push back software breakpoint for %s\n",
+			    "CSBB: %s stopped by software breakpoint\n",
 			    target_pid_to_str (lp->ptid));
 
       /* Back up the PC if necessary.  */
@@ -2846,7 +2853,7 @@ check_stopped_by_breakpoint (struct lwp_info *lp)
     {
       if (debug_linux_nat)
 	fprintf_unfiltered (gdb_stdlog,
-			    "CB: Push back hardware breakpoint for %s\n",
+			    "CSBB: stopped by hardware breakpoint %s\n",
 			    target_pid_to_str (lp->ptid));
 
       lp->stop_pc = pc;
@@ -3206,28 +3213,28 @@ linux_nat_filter_event (int lwpid, int status)
   if (lp->signalled
       && WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP)
     {
-      if (debug_linux_nat)
-	fprintf_unfiltered (gdb_stdlog,
-			    "LLW: Delayed SIGSTOP caught for %s.\n",
-			    target_pid_to_str (lp->ptid));
-
       lp->signalled = 0;
 
-      if (lp->last_resume_kind != resume_stop)
+      if (lp->last_resume_kind == resume_stop)
 	{
-	  /* This is a delayed SIGSTOP.  */
+	  if (debug_linux_nat)
+	    fprintf_unfiltered (gdb_stdlog,
+				"LLW: resume_stop SIGSTOP caught for %s.\n",
+				target_pid_to_str (lp->ptid));
+	}
+      else
+	{
+	  /* This is a delayed SIGSTOP.  Filter out the event.  */
 
-	  linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
 	  if (debug_linux_nat)
 	    fprintf_unfiltered (gdb_stdlog,
-				"LLW: %s %s, 0, 0 (discard SIGSTOP)\n",
+				"LLW: %s %s, 0, 0 (discard delayed SIGSTOP)\n",
 				lp->step ?
 				"PTRACE_SINGLESTEP" : "PTRACE_CONT",
 				target_pid_to_str (lp->ptid));
 
+	  linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
 	  gdb_assert (lp->resumed);
-
-	  /* Discard the event.  */
 	  return NULL;
 	}
     }